Multi-channel amplifier having programmable operational characteristics controlled with a serial interface

ABSTRACT

An amplifier having programmable operational characteristics and a serial communications interface is fabricated on an integrated circuit (IC). The serial communications interface controls the operational characteristics, e.g., gain, frequency response, etc., of the amplifier. A multiplexer (MUX) may also be included on the IC and may be controlled by the serial communications interface. Status of the amplifier may also be obtained through the serial communications interface. The pin count of the IC package may be kept to a minimum by using the serial communications interface.

RELATED PATENT APPLICATION

This application is a continuation-in-part of and claims priority tocommonly owned U.S. patent application Ser. No. 10/374,016, filed Feb.25, 2003, now U.S. Pat. No. 6,847,904 issued Jan. 25, 2005; entitled“Multi-Channel Programmable Gain Amplifier Controlled with a SerialInterface,” by Kumen E. Blake and James B. Nolan; which is herebyincorporated by reference herein for all purposes.

TECHNICAL FIELD OF THE INVENTION

The present invention generally relates to integrated circuitprogrammable gain amplifiers, and more particularly to an integratedcircuit multi-channel programmable gain amplifier having operationalcharacteristics controlled with a serial interface.

BACKGROUND OF THE RELATED TECHNOLOGY

Programmable gain amplifiers (PGAs) may be used to amplify analogsignals from sensors that measure, for example, temperature, pressure,humidity, vibration, pH, flow, etc. Usually, the amplified signals ofthe sensors are coupled to an analog-to-digital converter (ADC) whichsamples the analog signal values. The ADC digital output may be coupledto a digital signal processor (DSP) for further processing of theamplified signal information from these sensors.

The various sensors may require sampling at different rates sincefast-changing signals must be processed more frequently thanslower-changing signals (e.g., Nyquist sampling rate). In addition,different sensors may produce signals having different amplitudes thatrequire different amplifier gains so as to fully utilize the dynamicrange of the ADC.

A PGA typically switches resistance values in its feedback circuit toselect different gains. There also may be an analog input multiplexer(MUX) for selecting between a multiple number of analog input channelsto the PGA. In a microcontroller system it is therefore necessary tocontrol the gain switches and the analog input MUX to the PGA. Inaddition, it is useful to be able to send various other commands to thePGA, e.g., bandwidth, power draw, auto-calibrate, auto-offset zero,etc., and/or to read back the status or other data pertaining tooperation of the PGA and/or the MUX.

PGAs have been built using discrete amplifiers, resistors, switches andMUXs. However, the resulting system has been costly in terms of printedcircuit board space, power consumption and the number of discretecomponents required. Performance has also suffered because of componentmismatch, circuit drift and parasitic capacitances. Some integratedcircuit (IC) implementations have been developed for a PGA, but thesePGA ICs lack flexible control and do not have multiple input channelcapabilities for handling a plurality of sensors. Without multiple inputchannel capabilities, system-level calibration of gain and offset is notpossible since there can be no dedicated input channel for calibrationto a reference signal.

Presently, discrete logic inputs are used in PGA ICs to control the PGAfunctions, including gain. For example, three input pins of the PGA ICmay be dedicated to selecting one of eight gain settings. Other pins maybe used for device selection, power-down sleep mode, read status, writecontrol data, etc. However, these control and status pins of the PGA ICadd additional pin count to the IC device, increasing the IC packagesize and cost.

SUMMARY OF THE INVENTION

Therefore, there is a needed for flexible control, configuration anddetermining status of an integrated circuit (IC) amplifier havingprogrammable operational characteristics, e.g., programmable gainamplifier (PGA), without having to materially increase the pin count ofthe integrated circuit package.

The invention overcomes the above-identified problems as well as othershortcomings and deficiencies of existing technologies by providing anintegrated circuit (IC) amplifier having programmable operationalcharacteristics, e.g., programmable through a serial communicationsinterface that is adapted to communicate with the amplifier control andstatus circuits, and, in addition, to control an analog input MUX incombination with the amplifier in the IC package.

In accordance with an exemplary embodiment of the present invention, anamplifier, e.g., at least one operational amplifier, having programmableoperational characteristics and a serial communications interface arefabricated on an IC. The serial communications interface, e.g., serialperipheral interface (SPI), Inter-Integrated Circuit (I²C), SystemManagement Bus (SMBus) and the like, may be used to control theprogrammable operational characteristics of the amplifier, e.g., gain,bandwidth, power consumption, input offset correction, frequencyresponse, high pass filter frequency cutoff, low pass filter frequencycutoff, band pass filter frequency, phase delay, quality (Q), etc.Preferably, the operational characteristics setting elements, e.g., gainand/or frequency setting resistors, diodes, transistors, capacitorsand/or inductors for the programmable operational characteristicsamplifier, and programmable operational characteristics setting elementselection switches, e.g., diodes, transistors (bipolar, field effect,etc., preferably metal oxide semiconductor field effect—MOSFET), may bepart of the IC. It is contemplated and within the scope of the inventionthat any of the operational characteristics setting elements (e.g.,resistors, diodes, transistors, capacitors and/or inductors) of theamplifier, and/or operational characteristics setting element selectionswitches may be located off of the IC. The operational characteristicssetting element selection switches may be positioned between theoperational characteristics setting elements and the high-impedanceinverting input of the at least one operational amplifier for reducingdistortion, increasing bandwidth, frequency response shaping andimproving gain accuracy.

In accordance with another exemplary embodiment of the presentinvention, an amplifier, e.g., at least one operational amplifier,having programmable operational characteristics, an analog inputmultiplexer (MUX) and a serial communications interface are fabricatedon an IC. The serial communications interface, e.g., serial peripheralinterface (SPI), Inter-Integrated Circuit (I²C), System Management Bus(SMBus) and the like, may be used to control the programmableoperational characteristics of the amplifier, e.g., gain, bandwidth,power consumption, input offset correction, frequency response, highpass filter frequency cutoff, low pass filter frequency cutoff, bandpass filter frequency, phase delay, and quality (Q), etc., and selectsthe analog input channel of the MUX that is connected to the amplifieranalog input. Preferably, the operational characteristics settingelements, e.g., gain and/or frequency setting resistors, diodes,transistors, capacitors and/or inductors for the amplifier, andoperational characteristics setting element selection switches, e.g.,diodes, transistors (bipolar, field effect, etc., preferably metal oxidesemiconductor field effect—MOSFET), may be part of the IC. It iscontemplated and within the scope of the invention that any of theoperational characteristics setting elements (e.g., resistors, diodes,transistors, capacitors and/or inductors) for the programmableamplifier, and/or operational characteristics setting element selectionswitches may be located off of the IC. The operational characteristicssetting element selection switches, e.g., diodes, transistors (bipolar,field effect, etc., preferably metal oxide semiconductor fieldeffect—MOSFET), may be positioned between the operationalcharacteristics setting elements and the high-impedance inverting inputof the operational amplifier for reducing distortion, increasingbandwidth, frequency response shaping and improving gain accuracy.

The serial peripheral interface (SPI) requires only three pins of theIC, e.g., CS (chip select, active low), SCK (serial clock input) and SI(serial data input) to communicate with, for example, a microcontroller.Data and commands are sent to the programmable operationalcharacteristics amplifier and/or the MUX by appropriate timing on thesethree pins. In general, data may be shifted into the programmableoperational characteristics amplifier control circuits when CS is lowand SCK toggles. When SCK changes its logic level (e.g., rising orfalling edge of the clock waveform), data on the SI pin is shifted intothe amplifier control circuit. This data may be latched in the amplifiercontrol circuit and acted upon at the rising edge of the signal on theCS pin. The serial communications interface saves valuable pin count onthe IC package and printed circuit board real estate.

In addition, a serial data output (SO) pin is optional to allow daisychaining to other peripheral devices, each using the same CS signal.This saves additional chip select pins on the microcontroller package.In a similar fashion, the Inter-Integrated Circuit (I²C) may be used forcontrol and status of the programmable operational characteristicsamplifier and/or MUX. The serial communications interface is well suitedfor communicating with digital processor-based systems, e.g.,microprocessor, microcontroller, digital signal processor (DSP),programmable logic array (PLA), application specific integrated circuit(ASIC) and the like.

The present invention may be one or more integrated circuit diceun-packaged on a leadframe or substrate, or encapsulated in a plastic,epoxy and/or ceramic integrated circuit package, e.g., PDIP, SOIC, MSOP,TSSOP, QSOP and the like.

According to an exemplary embodiment of the present invention, anintegrated circuit amplifier having programmable operationalcharacteristics, comprises: at least one operational amplifier;operational characteristics setting elements for setting the operationalcharacteristics of the at least one operational amplifier; operationalcharacteristics setting element selection switches coupled between theoperational characteristics setting elements and the at least oneoperational amplifier; and a serial communications interface, whereinthe serial communications interface controls the operationalcharacteristics setting element selection switches. The integratedcircuit programmable operational characteristics amplifier may furthercomprise an analog multiplexer having a plurality of analog inputs andan analog output, the analog output coupled to an input of at least oneoperational amplifier. The integrated circuit programmable operationalcharacteristics amplifier may further comprise an analog multiplexerhaving a plurality of analog inputs and a plurality of analog outputs,the plurality of analog outputs coupled to inputs of respective ones ofthe at least one operational amplifiers. The analog multiplexer may becontrolled by the serial communications interface. The integratedcircuit programmable operational characteristics amplifier may furthercomprise a power-on-reset circuit for setting the serial communicationsinterface to a predetermined state. The integrated circuit programmableoperational characteristics amplifier may further comprise a memorycoupled to the serial communications interface. The memory may bevolatile and/or non-volatile.

According to another exemplary embodiment of the present invention, amethod for controlling an integrated circuit amplifier havingprogrammable operational characteristics, comprises an operationalamplifier, operational characteristics setting elements for determiningoperational characteristics of the operational amplifier, operationalcharacteristics setting element selection switches for coupling theoperational characteristics setting elements to the operationalamplifier and a serial communications interface, said method comprisingthe step of controlling the operational characteristics setting elementselection switches with the serial communications interface, andselecting the operational characteristics setting elements to be coupledto the operational amplifier with the operational characteristicssetting element selection switches, whereby the operational amplifieroperational characteristics are determined with the serialcommunications interface. The method may further comprise the step ofcontrolling the operational amplifier power consumption with the serialcommunications interface. The method may further comprise the steps ofcontrolling the operational amplifier bandwidth with the serialcommunications interface. The method may further comprise the step ofcontrolling the operational amplifier input offset correction with theserial communications interface. The method may further comprise thestep of controlling the operational amplifier frequency response withthe serial communications interface. The method may further comprise thestep of controlling a plurality of analog inputs to the operationalamplifier with a multiplexer (MUX) controlled by the serialcommunications interface. The step of controlling the characteristics ofthe operational amplifier may comprise the steps of: controlling theoperational characteristics selection switches with the serialcommunications interface; and selecting the operational characteristicssetting elements to be coupled to the operational amplifier with theoperational characteristics setting element selection switches.

According to still another exemplary embodiment of the presentinvention, a method for controlling an integrated circuit amplifierhaving programmable operational characteristics, comprises a pluralityof operational amplifiers, operational characteristics setting elementsfor determining operational characteristics for each of the plurality ofoperational amplifiers, operational characteristics setting elementselection switches for coupling the operational characteristics settingelements to respective ones of the plurality of operational amplifiersand a serial communications interface, said method comprising the stepof controlling the plurality of operational amplifier operationalcharacteristics with the serial communications interface. The method mayfurther comprise the step of controlling power consumption of each ofthe plurality of operational amplifiers with the serial communicationsinterface. The method may further comprise the step of controllingbandwidth for each of the plurality of operational amplifiers with theserial communications interface. The method may further comprise thestep of controlling input offset correction for each of the plurality ofoperational amplifiers with the serial communications interface. Themethod may further comprise the step of controlling frequency responsefor each of the plurality of operational amplifiers with the serialcommunications interface. The method may further comprise the step ofcontrolling a plurality of analog inputs to each of the plurality ofoperational amplifiers with a multiplexer (MUX) controlled by the serialcommunications interface. The step of controlling the plurality ofoperational amplifier may comprise the steps of: controlling theoperational characteristics setting element selection switches with theserial communications interface; and selecting the operationalcharacteristics setting elements to be coupled to respective ones of theplurality of operational amplifiers with the operational characteristicssetting element selection switches.

According to yet another exemplary embodiment of the present invention,a system for analog signal processing with an amplifier havingprogrammable operational characteristics, comprises an operationalamplifier; operational characteristics setting elements for settingoperational characteristics of the operational amplifier; operationalcharacteristics setting element selection switches coupled between theoperational characteristics setting elements and the operationalamplifier; and a serial communications interface, wherein the serialcommunications interface controls the operational characteristicssetting element selection switches; an analog-to-digital converter,wherein an input of the analog-to-digital converter is coupled to anoutput of the operational amplifier; and a digital processor, whereinthe digital processor is coupled to the output of the analog-to-digitalconverter and to the serial communications interface. The system mayfurther comprise an analog multiplexer having a plurality of analoginputs and an analog output, the analog output coupled to an input ofthe operational amplifier. The analog multiplexer may be controlled bythe serial communications interface.

According to still another exemplary embodiment of the presentinvention, a system for analog signal processing with an amplifierhaving programmable operational characteristics, comprises a pluralityof operational amplifiers; operational characteristics setting elementsfor setting operational characteristics for each of the plurality ofoperational amplifiers; operational characteristics setting elementselection switches coupled between the operational characteristicssetting elements and the respective ones of the plurality of operationalamplifiers; and a serial communications interface, wherein the serialcommunications interface controls the operational characteristicssetting element selection switches; at least one analog-to-digitalconverter, wherein a respective input of the at least oneanalog-to-digital converter is coupled to an output of a respective onethe plurality of operational amplifiers; and a digital processor,wherein the digital processor is coupled to the output of the at leastone analog-to-digital converter and to the serial communicationsinterface. The system may further comprise an analog multiplexer havinga plurality of analog inputs and analog outputs, the plurality of analogoutputs coupled to respective inputs of the plurality of operationalamplifiers. The analog multiplexer may be controlled by the serialcommunications interface.

A technical advantage of the present invention is that it requires aminimum number of signal pins on an IC. Another technical advantage is asimple and standardized interface for controlling an amplifier havingprogrammable operational characteristics and/or MUX of an IC.

Features and advantages of the invention will be apparent from thefollowing description of the embodiments, given for the purpose ofdisclosure and taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING

A more complete understanding of the present disclosure and advantagesthereof may be acquired by referring to the following description takenin conjunction with the accompanying drawing, wherein:

FIG. 1 illustrates schematic block diagram of an exemplary embodiment ofthe present invention; and

FIG. 2 illustrates a schematic block diagram of an exemplary systemutilizing the embodiment of FIG. 1.

While the present invention is susceptible to various modifications andalternative forms, specific exemplary embodiments thereof have beenshown by way of example in the drawings and are herein described indetail. It should be understood, however, that the description herein ofspecific embodiments is not intended to limit the invention to theparticular forms disclosed, but on the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Referring now to the drawings, the details of exemplary embodiments ofthe present invention are schematically illustrated. Like elements inthe drawing will be represented by like numbers, and similar elementswill be represented by like numbers with a different lower case lettersuffix.

Referring to FIG. 1, depicted is a schematic block diagram of anexemplary embodiment of the present invention. An integrated circuitamplifier having programmable operational characteristics, e.g.,programmable gain amplifier (PGA), generally represented by the numeral100, comprises an operational amplifier 102, a multiplexer (MUX) 104, aserial peripheral interface (SPI) 106, operational characteristicssetting element selection switches 110, and operational characteristicssetting elements 112 (e.g., resistors, diodes, transistors, capacitorsand/or inductors) in an integrated circuit 114. The operationalamplifier 102 may be one or more operational amplifiers in theintegrated circuit 114, each of the one or more operational amplifiers102 having a output, V_(out). In addition the amplifier 100 may alsoinclude a power-on-reset (POR) 108 and/or a memory 116 (volatile and/ornon-volatile). The integrated circuit 114 may be one or more integratedcircuit dice on a leadframe (not illustrated) or may be a flip-chip ballbonded to a substrate (not illustrated).

The one or more integrated circuit dice may be un-encapsulated on theleadframe or substrate, or may be encapsulated in an integrated circuitpackage, e.g., PDIP, SOIC, MSOP, TSSOP, QSOP and the like.

Another exemplary embodiment of the present invention does not have theMUX 104 with the integrated circuit die 114. The SPI 106 may control theoperational amplifier 102 operational characteristics, e.g., gain,bandwidth, power consumption, input offset correction, frequencyresponse, high pass filter frequency cutoff, low pass filter frequencycutoff, band pass filter frequency, phase delay, and quality (Q), etc.The SPI 106 may also control input offset calibration, bandwidth,frequency response shaping, power utilization, etc., of the operationalamplifier 102. Optionally, the POR 108 may be used to reset andinitialize the SPI 106 to a predetermined state during power-up. The SPI106 may also operate under the serial peripheral interface (SPI),Inter-Integrated Circuit (I²C), System Management Bus (SMBus), or anyother serial standard desired.

An advantage of the present invention is that the SPI 106 only requiresthree external connections, thus minimizing pin count of the IC package.A chip select ( CS), for example, active low, a serial clock input (SCK)and a serial data input (SI) are all that are needed for completecontrol and status of the amplifier 100. Data and commands may be sentto the amplifier 100 by appropriate timing on these signal inputs. Forexample, data may be shifted into the amplifier 100 when CS is at a lowlogic level and SCK is allowed to toggle. At the rising edge of thesignal at SCK, data on the SI is shifted into the amplifier 100. Thisdata may be latched (latch not shown) and acted upon at the rising edgeof the signal at CS. In addition, a serial data output (SO) maybe usedfor daisy chaining to other peripheral devices (not shown) using thesame CS signal. This feature saves additional chip select connections tothe digital processor (not shown). Other variations of serial interfacesmay be, for example but not limited to, serial peripheral interface(SPI), Inter-Integrated Circuit (I²C), System Management Bus (SMBus) andthe like.

The SPI 106 may also control the MUX 104, illustrated with eight inputs,CH0–CH7, more or fewer inputs are also contemplated and within the scopeof the present invention. The MUX 104 is optional and the presentinvention may also function without a MUX, or may utilize an externalMUX, depending upon system requirements.

The operational characteristics setting element selection switches 110control selection of the operational characteristics setting elements112 and are generally positioned between the operational characteristicssetting elements (e.g., resistors, diodes, transistors, capacitorsand/or inductors) and the high-impedance inverting input of theoperational amplifier 102 to reduce distortion, increase bandwidth andimprove gain accuracy. The operational characteristics setting elements112 may also be coupled to a voltage reference, V_(REF), which may bepart of the integrated circuit die 114 or may be an external (off chip)voltage reference. More than one voltage reference may also be utilizedwith the present invention and is contemplated herein.

Referring to FIG. 2, depicted is a schematic block diagram of anexemplary system utilizing the embodiment of FIG. 1. The system,generally represented by the numeral 200, comprises the amplifier 100,an analog-to-digital converter (ADC) 220 and a digital processor 222.Illustrated is the amplifier 100 with eight analog inputs, CH0–CH7, andan analog output 216 coupled to an input of the ADC 220. The ADC 220 maybe any type of ADC known to those skilled in the art of analog todigital conversion. The ADC 220 has a digital output 218 coupled to thedigital processor 222. The digital processor 222 has a serial peripheralinterface coupled to over a serial bus 224 to the SPI 106 (FIG. 1). Aserial peripheral interface (SPI), Inter-Integrated Circuit (I²C),System Management Bus (SMBus) or any other type of serial interface mayalso be utilized, according to the present invention. The digitalprocessor 222 may be, for example, a microprocessor, a microcontroller,a digital signal processor (DSP), a programmable logic array (PLA), anapplication specific integrated circuit (ASIC) and the like.

The invention, therefore, is well adapted to carry out the objects andattain the ends and advantages mentioned, as well as others inherenttherein. While the invention has been depicted, described, and isdefined by reference to exemplary embodiments of the invention, such areference does not imply a limitation on the invention, and no suchlimitation is to be inferred. The invention is capable of considerablemodification, alteration, and equivalents in form and function, as willoccur to those ordinarily skilled in the pertinent arts and having thebenefit of this disclosure. The depicted and described embodiments ofthe invention are exemplary only, and are not exhaustive of the scope ofthe invention. Consequently, the invention is intended to be limitedonly by the spirit and scope of the appended claims, giving fullcognizance to equivalents in all respects.

1. A system for analog signal processing, said system comprising: anamplifier having programmable operational characteristics, the amplifiercomprising: an operational amplifier, operational characteristicssetting elements for setting operational characteristics of theoperational amplifier, operational characteristics setting elementselection switches coupled between the operational characteristicssetting elements and the operational amplifier, and a serialcommunications interface, wherein the serial communications interfacecontrols the operational characteristics setting element selectionswitches; an analog-to-digital converter, wherein an input of theanalog-to-digital converter is coupled to an output of the operationalamplifier; and a digital processor, wherein the digital processor iscoupled to the output of the analog-to-digital converter and to theserial communications interface.
 2. The system according to claim 1,wherein the serial communications interface is selected from the groupconsisting of a serial peripheral interface (SPI), an Inter-IntegratedCircuit bus interface, and a System Management Bus (SMBus) interface. 3.The system according to claim 2, wherein the serial peripheral interfacecomprises a chip select, a serial clock input and a serial data input.4. The system according to claim 3, wherein the serial peripheralinterface further comprises a serial data output.
 5. The systemaccording to claim 1, wherein the operational characteristics areselected from one or more of the group consisting of gain, high passfilter frequency cutoff, low pass filter frequency cutoff, band passfilter frequency, phase delay, and quality (Q).
 6. The system accordingto claim 1, further comprising a memory coupled to the serialcommunications interface.
 7. The system according to claim 6, whereinthe memory is volatile.
 8. The system according to claim 6, wherein thememory is non-volatile.
 9. The system according to claim 1, furthercomprising an analog multiplexer having a plurality of analog inputs andan analog output, the analog output coupled to an input of theoperational amplifier.
 10. The system according to claim 9, wherein theanalog multiplexer is controlled by the serial communications interface.11. The system according to claim 1, wherein the digital processor isselected from the group consisting of a microprocessor, amicrocontroller, a digital signal processor (DSP), a programmable logicarray (PLA) and an application specific integrated circuit (ASIC).
 12. Asystem for analog signal processing, said system comprising: anamplifier having programmable operational characteristics, the amplifiercomprising: a plurality of operational amplifiers, operationalcharacteristics setting elements for setting operational characteristicsfor each of the plurality of operational amplifiers, operationalcharacteristics setting element selection switches coupled between theoperational characteristics setting elements and the respective ones ofthe plurality of operational amplifiers, and a serial communicationsinterface, wherein the serial communications interface controls theoperational characteristics setting element selection switches; at leastone analog-to-digital converter, wherein a respective input of the atleast one analog-to-digital converter is coupled to an output of arespective one of the plurality of operational amplifiers; and a digitalprocessor, wherein the digital processor is coupled to the output of theat least one analog-to-digital converter and to the serialcommunications interface.
 13. The system according to claim 12, furthercomprising an analog multiplexer having a plurality of analog inputs andanalog outputs, the plurality of analog outputs coupled to respectiveinputs of the plurality of operational amplifiers.
 14. The systemaccording to claim 13, wherein the analog multiplexer is controlled bythe serial communications interface.
 15. The system according to claim12, wherein the digital processor is selected from the group consistingof a microprocessor, a microcontroller, a digital signal processor(DSP), a programmable logic array (PLA) and an application specificintegrated circuit (ASIC).
 16. The system according to claim 12,comprising at least one serial communications interface chosen from aserial peripheral interface (SPI), an Inter-Integrated Circuitinterface, and a System Management Bus (SMBus) interface.
 17. The systemaccording to claim 12, comprising at least one operationalcharacteristic chosen from gain, high pass filter frequency cutoff, lowpass filter frequency cutoff, band pass filter frequency, phase delay,and quality (Q).
 18. A integrated circuit amplifier having programmableoperational characteristics, the integrated circuit amplifiercomprising: a plurality of operational amplifiers, each one havinginverting and non-inverting inputs and an output; operationalcharacteristics setting elements for setting the operationalcharacteristics of each of the operational amplifiers; operationalcharacteristics setting element selection switches coupled between theoperational characteristics setting elements and the plurality ofoperational amplifiers; an analog multiplexer having a plurality ofanalog inputs and a plurality of analog outputs, the plurality of analogoutputs coupled to non-inverting inputs of respective ones of theplurality of operational amplifiers; and a serial communicationsinterface, wherein the serial communications interface controls theoperational characteristics setting element selection switches and theanalog multiplexer.
 19. The integrated circuit amplifier according toclaim 18, comprising at least one serial communications interface chosenfrom a serial peripheral interface (SPI), an Inter-Integrated Circuitbus interface, and a System Management Bus (SMBus) interface.
 20. Theintegrated circuit amplifier according to claim 19, wherein the serialperipheral interface comprises a chip select, a serial clock input and aserial data input.
 21. The integrated circuit amplifier according toclaim 20, wherein the serial peripheral interface further comprises aserial data input.
 22. The integrated circuit amplifier according toclaim 18, comprising at least one operational characteristics chosenfrom gain, high pass filter frequency cutoff, low pass filter frequencycutoff, band pass filter frequency, phase delay, and quality (Q). 23.The integrated circuit amplifier according to claim 18, furthercomprising an integrated circuit package.
 24. The integrated circuitamplifier according to claim 23, comprising at least one integratedcircuit package chosen from a flip-chip package, a plastic package, aneopxy package, and a ceramic package.
 25. The integrated circuitamplifier according to claim 24, comprising at least one integratedcircuit package chosen from PDIP, SOIC, MSOP, TSSOP and QSOP.
 26. Theintegrated circuit amplifier according to claim 18, further comprising apower-on-reset circuit for setting the serial communications interfaceto a predetermined state.
 27. The integrated circuit amplifier accordingto claim 26, further comprising a memory coupled to the serialcommunications interface.
 28. The integrated circuit amplifier accordingto claim 27, wherein the memory is volatile.
 29. The integrated circuitcircult amplifier according to claim 27, wherein the memory isnon-volatile.